Electric pencil sharpener

ABSTRACT

An electric pencil sharpener including an ON-OFF switch by means of which the sharpener can be adjusted to sharpen a pencil to a desired sharpness. The pencil sharpener is provided with a slidable rod which is adapted to be displaced by the pencil lead tip as the pencil is being sharpened, the slidable rod being so arranged that its displacement is effective to actuate another switch to automatically stop the motor of the sharpener.

United States Patent Hori [ 51 Mar. 21, 1972 [541 ELECTRIC PENCIL SHARPENER [72] Inventor: Takeo Hori, Fukuoka-shi, Japan [73] Assignee:

Osaka, Japan [22] Filed: Sept. 16, 1969 211 App]. No.: 858,469

[30] Foreign Application Priority Data Sept. 20, 1968 Japan ...43/69026 521 U.s.cl....l ..144 2s.s,144/2s.72 51 Int. Cl ..B43l23/02 [58] FieldofSearch ..144/28.72,28.5,28.6, 28, 144/283, 28.4

Matsushita Electric Industrial Co., Ltd.,

[56] References Cited UNITED STATES PATENTS 2,408,767 10/1946 Fleming ..144/2s.s 2,561,438 7/1951 Duchesneau .....l44/28.5 3,486,540 12/1969 Hori ..l44/28.72

Primary ExaminerAndrew R. Juhasz Assistant ExaminerJames F. Coan Attorney-Stevens, Davis, Miller & Mosher ABSTRACT An electric pencil sharpener'including an ON-OFF switch by means of which the sharpener can be adjusted to sharpen a pencil to a desired sharpness. The pencil sharpener is provided with a slidable rod which is adapted to be displaced by the pencil lead tip as the pencil is being sharpened, the slidable rod being so arranged that its displacement is effective to actuate another switch to automatically stop the motor of the sharpener.

4 Claims, 13 Drawing Figures P atented March 21 1912 3,650,308

' 5 Sheets-Sheet 1 INVENTOR BY $710M, M M/ fi ATTORNEKS' Patented March 21, 1972 3,650,308

' 5 Sheets-Sheet 2 7 6 27 lllllllllln Patented Marc::h 21, 1912 3,650,308

5 Sheets-Sheet 3 ELECTRIC PENCIL SHARPENER The present invention belongs to the field of electric pencil sharpeners which may be used in homes, schools, offices and the like, and relates to an electric pencil sharpener provided with an ON-OFF switch which can be operated as desired so that the sharpness of the sharpened tip of the pencil lead can be adjusted in accordance with the purpose for which the pencil is used.

Conventional electric pencil Sharpeners include such a type in which the rotation of the driving motor is stopped when a pencil lead is sharpened, or in which a lamp is provided for indicating that the pencil lead is sharpened. However, in these conventional electric pencil sharpeners, when it is desired to obtain a relatively obtuse lead tip, a pencil which is being sharpened must be frequently withdrawn from the sharpener in order to seen the sharpness of the lead tip. Further, in an electric pencil sharpener, since a sharpening operation can be finished in a relatively short period, such as two seconds, a pencil lead is often over-sharpened when it is withdrawn from the sharpener to seen the sharpness of lead tip. Thus, the conventional pencil sharpener is disadvantageous in that it is not effective to obtain a desired sharpness of lead tip unless the sharpening operation is carried out with extreme care.

According to the present invention, there is provided an electric pencil sharpener comprising a motor having a power switch which is adapted to be closed when a pencil is inserted into the sharpener for energizing the motor, a cutter rotatably driven by said motor to sharpen the pencil, a sliding rod adapted to be slidingly moved by the lead tip of the pencil a second switch disposed at the rear end of said sliding rod and having three contact elements, and a third switch mounted on a casing, the ON-OFF actuation of said third switch being effective to determine the sharpness of the pencil lead tip, the power switch and the second and the third switches being operatively connected with .each other, and all of said components being housed within an upper and a lower casings.

The first object of the present invention is to provide, in an electric pencil sharpener, an ON-OFF switch through actuation of which the sharpener can be adjusted in two stages so that either a relatively obtuse or relatively sharp pencil lead tip can be obtained.

The second object of the present invention is to provide means for automatically stopping the sharpener when a pencil lead tip is sharpened to a relatively obtuse shape as well as means for automatically stopping the sharpener when the pencil lead tip is sharpened to a relatively sharp shape.

The third object of the present invention is to provide a slidable rod which is adapted to be pushed by the tip of the pencil lead as the pencil is advanced when it is being sharpened by the cutter, whereby the sharpness of the lead tip is transferred to the displacement of the slidable rod.

The fourth object of the present invention is to provide, in opposite relation to the sliding plate, a switch having three contact elements which are sequentially actuated in response to the displacement of the slidable rod so that the motor is automatically stopped when a predetermined sharpness of the pencil lead tip is obtained.

The fifth object of the present invention is to provide three contact elements comprising a button side, an intermediate and an anti-button side contact elements which are maintained in normally engaged position and actuated by a button which is disposed opposite to the slidable rod.

The sixth object of the present invention is to automatically stop the motor with a relatively obtuse pencil lead tip by disengagement of the button side contact element and the intermediate contact element and to automatically stop the motor with a relatively sharp pencil lead tip by disengagement of the intermediate contact element and the anti-button side contact element.

The seventh object of the present invention is to secure on the intermediate contact element a button which cooperates with the slidable rod adapted to be pushed by the pencil lead tip, so that the motor is automatically stopped by disengagement of the intermediate contact element and the button side contact element when the pencil lead tip is sharpened to a relatively obtuse shape, and to automatically stop the motor by short circuiting the auxiliary winding of the condensor-run motor through engagement of the intermediate contact element and the anti-button side contact element when the pencil lead tip is sharpened to a relatively sharp shape.

The eighth object of the present invention is to secure on the button side contact element a button which is adapted to be pushed by the pencil lead tip and maintain the button side, the intermediate and the anti-button side contact elements apartfrom each other, whereby the motor is automatically stopped when the lead tip is sharpened to a relatively obtuse shape by short circuiting the auxiliary windings of the condensor-run motor through engagement of the intermediate contact element and the button side contact element, and the motor is automatically stopped when the pencil lead tip is sharpened to a relatively sharp shape by short circuiting the auxiliary winding of the condensor-run motor by putting all of said three contact elements into contact together.

The present invention will now be described with reference to the preferred embodiments which are illustrated in the accompanying drawings, in which;

FIG. 1 is a side view of an electric pencil sharpener made in accordance with the present invention, a portion of the sharpener being shown by a section;

FIGS. 2A, 2B and 2C show the operation of switch mechanism employed in the first embodiment;

FIG. 3 is an electric circuit diagram of the switch mechanism shown in FIGS. 2A, 2B and 2C;

FIGS. 4A, 4B and 4C show the operation of switch mechanism employed in the second embodiment;

FIG. 5 is an electric circuit diagram of the switch mechanism shown in FIGS. 4A, 4B and 4C;

FIGS. 6A, 6B and 6C show the operation of switch mechanism employed in the third embodiment; and,

FIG, 7 is an electric circuit diagram of the switch mechanism shown in FlGS. 6A, 6B and 6C.

Referring first to FIGS. 1, 2A, 2B, 2C and 3, the reference numeral 1 shows a cutter holder carried by a bearing portion 6 of a frame 5 and rotatably supporting a cutter 4 which has a pinion gear 3 secured thereto. The pinion gear 3 is arranged to mesh with an internal gear 2. A motor 7 is so arranged that its rotation is transmitted to the cutter holder 1 through a pair of gears 8 and 9. At the front portion of the cutter holder 1, there is disposed a power switch 11 which is actuated by a pencil 10 inserted into the cutter holder 1 to close an electric circuit for energizing the motor 7 and is opened when the pencil 10 is withdrawn. Further, in front of the power switch 11, there is disposed a mouth piece 13 which has a central hole 12 for inserting a pencil. The reference numeral 14 shows a slidable rod which is slidably received in a through hole 16 concentrically provided in a drive shaft 15 of the cutter holder 1. The slidable rod 14 is provided at its front end with a cut 17 along the outer surface of the cutter 4 and secured in position against rotation by a stop plate 18 engaged with the bottom portion of the cut out 17. The reference numeral 19 shows a motor control switch disposed so as to be abutted by the rear end of said slidable rod 14. The switch 19 is arranged so as to be actuated by the slidable rod 14 when the rod is slidably displaced by the tip end 20 of the pencil 10 which is being sharpened. The reference numeral 21 shows an ON-OFF switch provided on an upper casing 22 and adapted to be actuated from the outside to adjust the sharpness of the sharpened lead tip. Further, the numeral 23 shows a lower casing, 24 a box for receiving pencil shavings and 25 foot rubbers.

The construction of said motor control switch 19 will now be described in detail. The switch 19 includes a switch housing 26 which is provided at one of its side walls with a through hole 27 through hole 27 through which a button 28 passes. Within the housing 26, there are disposed, from the side near to the side wall having the hole 27 for inserting the button 28, a button side contact element 29, an intermediate contact element 30 and an anti-button side contact element 31, the elements 29, 30 and 31 being normally maintained in contact with each other at one end. The other end of each element is secured to the housing wall and projects from the housing 26.

These contact elements 29, 30 and 31 comprises substantially straight button-side and intermediate contact elements 29 and 30 and an anti-button side contact element 31 which is bent toward the button so as to provide a spring pressure which is sufficient to effect the engagement between the antibutton side contact element 31 and the intermediate contact element 30 and also to deform the intermediate contact element 30 into contact with the button side contact element 29.

The button 28 is biased by means of a spring 32 acting one of its ends toward the direction to open the contact elements. One end of the button 28 is in an abutting engagement with the rear end of the slidable rod 14 through a plate 33 and the other end is in engagement with the anti-button side contact element 31 without interferring with any of the intermediate contact element 30 and the button side contact element 29 which are shorter'than the anti-button side contact element 31. In operation of the switch 19, when the button 28 is pressed through the plate 33 to displace the anti-button side contact 31 which is in abutting engagement with the button 28, the intermediate contact element 30 which has been depressed by the spring pressure of the anti-button side contact element 31 is allowed to return apart from the button side contact element 29 until it retains its initial straight shape, and as the anti-button side contact element 31 is further displaced, it is disengaged from the intermediate contact element 30. Thus all of the contact elements are disengaged from each other. Referring to the electric circuit, the button side contact element 29 is connected with one of the terminals of plug 34, and the intermediate contact element 30 is connected with said terminal of the plug 34 through the ON-OF F switch 21 for adjusting the sharpness of the pencil lead tip. The anti-button side contact element 31 is connected with one end of the motor 7, the other end of the motor 7 being connected with the other terminal of the plug 34. Further, the motor 7 comprises a main coil 35, an auxiliary coil 36 and a condenser 37.

The operation of the above embodiment will now be described. When a pencil 10 to be sharpened is inserted into the hole 12 of the mouth piece 13, the power switch 11 is closed as shown in FIG. 2A, and since the contact elements 29, 30 and 31 of the switch 19 are in contact with each other, the motor 7 is started to rotate so that the cutter holder 1 is rotated to sharpen the pencil 10. When it is desired to obtain a relatively obtuse lead tip, the switch 21 is opened as shown by a solid line in FIG. 2A. As the sharpening operation operation progresses and the lead tip 20 is sharpened as shown in FIG. 2B, the slidable rod 14 is slidably moved by the lead tip 20. As a result, the button 28 of the switch 19 is displaced and causes the intermediate and the button side contact elements 30 and 29 to move from each other. Thus, the electric current to the motor 7 is interrupted and the motor 7 is stopped. Thereafter, the pencil 10 is withdrawn from the sharpener and thus a pencil which is sharpened to have a relatively obtuse lead tip can be obtained. When it is desired to obtain a pencil of a relatively sharp lead tip, the switch 21 is closed as shown by a broken line in FIG. 2A. In this case, even when the pencil 10 is sharpened to such a degree that the intermediate and the button side contact elements 30 and 29 are disengaged from each other, the motor 7 is supplied with current through the switch 21, the intermediate contact element 30 and the anti-button side contact element 31, so that the motor 7 continues to rotate and the sharpening of the pencil 10 is continued. As the lead tip 20 of the pencil 10 is further sharpened as shown in FIG. 2C, the slidable rod 14 is further displaced by the lead tip 20 to cause a further displacement of the button 28, whereby the anti-button side contact element 31 is disengaged from the intermediate contact element 30. Thus, the current to the motor 7 is interrupted and the motor 7 is caused to stop. Thereafter, the pencil 10 is withdrawn and thus a pencil having a relatively sharp lead tip can be obtained. As described above, by selecting the position of the switch 21, the motor 7 can be stopped with either a relatively obtuse or a relatively sharp lead tip 20. Thus, a pencil having either a relatively obtuse or sharp lead tip can be obtained as desired.

The second embodiment shown in FIGS. 4A, 4B, 4C and 5 will now be described. Since the mechanical parts of this embodiment are identical to those in the previous embodiment, their detail will not be described and the parts in this embodi ment will be identified by the same reference numerals as in the corresponding parts in the previous embodiment. Refer: ring to the motor control and the electric circuit, the switch 38 includes a substantially straight button side contact element 40, an intermediate contact element 41 and an anti-button side contact element 42 which are disposed within a housing 39.'The intermediate contact element 41 is in an abutting engagement with a button 43 and the button side contact element 40 is normally maintained in contact with the intermediate contact element 41 and disposed so as not to interfere with the button 43. Each of the contact elements has one end secured to the housing wall and projecting from the housing 39. One end of the button 43 abuts a plate 44 which is pivotally mounted on the switch housing at its one end and biased by means of a coil spring 45 toward the rear end of the slidable rod 14. In operation of the switch 38, the button 43 is displaced through the plate 44 to bend the intermediate contact element 41. As the result, the intermediate contact element 41 is moved apart from the button side contact element 40. As the button 43 is further displaced, the intermediate contact element 41 is further bent and contacts with the antibutton side contact element 42. Referring to the electric circuit, the button side contact element 40 is connected with one of the terminals of the plug 34, and the intermediate contact element 41 is connected with one end (a wire common to the main and the auxiliary windings) of the motor 7 and through an ON-OFF switch 21 for adjusting the sharpness of the pencil lead tip with said terminal of the plug 34. The other end of the motor 7 is connected through the power switch 11 to the other terminal of the plug 34. The anti-button side contact element 42 is connected with the motor 7 at a point between the auxiliary coil 36 and the condenser 37.

Referring now to motor, a motor for use with an electric pencil sharpener can be a relatively small one and does not require a high starting torque. For this purpose, a condenser run motor is usually employed. The condenser run motor is rotated by a torque given by the main coil as well as a torque given by the auxiliary coil, so that when the auxiliary coil is interrupted or short circuited and the torque of the auxiliary coil is nullified, the motor torque is decreased. Therefore, if the motor is subjected to a load or, in case of an electric pencil sharpener, if a pencil is being sharpened, the rotation of the motor will be stopped.

When the auxiliary coil is short circuited, the current is suppressed by an impedance of the condenser so that no practical problem will occur. In one example, a motor having a condenser of 3.5 [LF was operated with a current of 60 Hertz per second with the auxiliary coil short circuited. The measured short circuit current was only 0.13 amperes.

The operation of the second embodiment will now be described. When a pencil 10 to be sharpened is inserted into the hole 12 of the mouth piece 13, the power switch 11 is closed as shown in FIG. 4A. Then, since the button side contact element 40 and the intermediate contact element 41 of the switch 38 are in contact with each other, the motor 7 is caused to rotate and thus the cutter holder 1 is rotated to start sharpening operation. When it is desired to obtain a relatively obtuse pencil lead tip, the switch 21 is opened as shown by a solid line in FIG. 4A. Then, as the lead tip 20 of the pencil 10 is sharpened as shown in FIG. 4B, the slidable rod 14 is pushed by the lead tip 20. As the result, the button 43 of the switch 38 is displaced through the plate 44 and the intermediate contact element 41 is disengaged from the button side contact element 40. Thus, the current to the motor 7 is interrupted and the motor 7 is stopped. Thereafter, the pencil 10 is withdrawn and thus a pencil having a relatively obtuse lead tip can be obtained. When it is desired to obtain a sharp pencil lead tip, the switch 21 is closed as shown by a broken line in FIG. 4A. Then, even when the pencil is sharpened to such a degree that the intermediate contact element 41 of the switch 38 is disengaged from the button side-contact element, the motor 7 is continuously supplied with current and the motor 7 continues to rotate to effect the sharpening operation. As the lead tip of the pencil 10 is further sharpened as shown in FIG. 4C, the slidable rod 14 is further displaced by. the lead tip 20, and the button 43 of the switch 38 is further moved until the intermediate contact element 41 engages with the anti-button side contact element 42. Thus, the auxiliary coil 36 of the motor 7 is short circuited and the motor torque is decreased to such a degree that the motor 7 is stopped. Then, the pencil 10 is withdrawn and a pencil having a relatively sharp lead tip can be obtained.

As described above, by selecting the position of the switch 21, the motor 7 can be stopped when a relatively obtuse or sharp lead tip 20 is obtained, whereby a desired sharpness of the lead tip can be obtained.

The third embodiment of the present invention will now be described with reference to FIGS. 6A, 6B, 6C and 7. The mechanical parts of this embodiments are identical to those in the preceding embodiments so that they will not be described in detail, and the corresponding parts thereof are identified by the same reference numerals as those in the preceding embodiments. The motor control switch and its electric circuit will now be described. The switch 46 has a substantially straight button side contact element 48, an intermediate contact element 49 and an anti-button side contact element 50 which are disposed in a housing 47. The contact elements 48, 49 and 50 are normally maintained apart from each other, and each of them is secured at its one end to the housing wall and projects from the housing 47. One end of the button 51 is in engagement with the button side contact element 48 and the other end contacts with a plate 53 which is biased by a spring 52 toward the rear end of the slidable rod 14.

In operation of the switch, the button 51 is moved through the plate 53 whereby the button side contact element 48, the intermediate contact element 49 and the anti-button side contact element 50 are sequentially brought into mutual contact. Referring now to the electric circuit, the button side contact element 48 is connected to one end (a lead wire common to the main and the auxiliary windings) of the motor 7 and one of the terminals of the plug 34. The other end of the motor 7 is connected through the switch 11 to the other terminal of the plug 34. The anti-button side contact element 50 is connected to the motor 7 at a point between the auxiliary coil 36 and the condenser 37, and the intermediate contact element 49 is connected through the ON-OFF switch 21 to the motor 7 at said point between the auxiliary coil 36 and the condenser 37.

The operation of this embodiment will now be described. When a pencil to be sharpened is inserted into the hole 12 of the mouth piece 13, the power switch 11 is closed as shown in FIG. 6A and the motor 7 is started to rotate, so that the cutter holder 1 is rotated and the sharpening operation is started. When it is desired to obtain a relatively obtuse pencil lead tip, the switch 21 is opened as shown by a solid line in FIG. 6A. As the lead tip 20 of the pencil 10 is sharpened as shown in FIG. 6B, the sliding rod 14 is slidingly moved by the lead tip 20. As the result, the button 51 of the switch 46 is displaced through the plate 53 until the button side contact element 48 and the intermediate contact element 49 are brought into contact with each other. Then, the auxiliary coil 36 of the motor 7 is short circuited and the motor torque is decreased to such a degree that the rotation of the motor 7 is stopped. Thereafter, the pencil 10 is withdrawn from the sharpener and thus a pencil having a relatively obtuse lead tip can be obtained. Further, when it is desired to obtain a relatively sharp pencil lead tip, the switch 21 is closed as shown by a broken line in FIG. 4A. Then, even when the pencil 10 is sharpened to such a degree that the button side contact element 48 of the switch 46 is brought into contactwith the intermediate contact element 49, the auxiliary coil 36 is not short circuited since the switch 21 is open, and thus the motor 7 continues to rotate and the sharpening operation is continued. As the lead tip 20 is further sharpened as shown in FIG. 6C, the slidable rod 14 is further moved by the lead tip 20 to further displace the button 51 of the switch 46, so that the intermediate contact element 49 is brought into contact with the anti-button side contact element 50. Thus, even if the switch 21 is open, the auxiliary coil 36 is short circuited and the motor torque is decreased to such a degree that the rotation of the motor 7 is stopped. Thereafter, the pencil 10 is withdrawn from the sharpener and thus a pencil having a relatively sharp lead tip can be obtained. Thus, by selecting the position of the switch 21, the motor 7 can be stopped with either a relatively obtuse or sharp lead tip 20, and a desired sharpness can be'obtained.

As described above, according to the present invention, a motor control switch having a plurality of contact elements sequentially operated by the lead tip of a pencil to be sharpened is combined with another externally actuated switch for nullifying the function of the first stage of said motor control switch, whereby only by selecting the position of the second mentioned switch, the sharpener can be automatically stopped with either a relatively obtuse pencil lead tip or a relatively sharp lead tip. Since the operation only requires to actuate the second mentioned switch, the operation is very simple, and since all operation is performed electrically, a reliable operation can be obtained. Further, according to the present invention, since the motor is automatically stopped when a pencil is sharpened to a desired sharpness, a pencil of desired sharpness can positively be obtained. Further, the automatic stop feature of the present invention is effective to prevent over-sharpening. Still further, the structure comprising in combination two switches and a motor can be made very simple and less expensive. Thus the present invention is very advantageous over conventional electric pencil sharpeners.

What we claim is:

1. An electric pencil sharpener, comprising:

a motor;

a cutter holder rotatably driven by said motor;

a cutter member secured to said holder to rotate therewith;

a slidable rod disposed along the axis of said cutter holder, said slidable rod being displaceable by the tip of a pencil to be sharpened;

a first switch disposed rearwardly of and contactable by said slidable rod, said first switch having three contact elements sequentially operated by said rod, said first switch being connected to said motor to control operation thereof;

a second switch connected between an external power source and said first switch;

wherein:

a. in a first position of said second switch and first and second positions of said first switch, said motor is in an operative mode;

b. in said first position of said second switch and a third position of said first switch, said motor is in an inoperative mode;

c. in a second position of said second switch and in said first position of said first switch, said motor is in said operative mode; and

d. in said second position of said second switch and in said second and third positions of said first switch, said motor is in said inoperative mode.

2. An electric pencil sharpener according to claim 1, wherein in said first position of said first switch all three contact elements contact each other, in said second position of said first switch only two of said contact elements contact each other and in said third position of said first switch none of said contact elements contact each other.

3. An electric pencil sharpener according to claim 1, wherein in said first position of said first switch and second of said contact elements contact each other, the third element first position of said first switch said three contact elements are disengaged from contact with each other, in said second position of said first switch, first and second of said contact elements are engaged with each other, the third element being disengaged from contact with said first and second elements, and in said third position of said first switch said first, second and third contact elements are in contact with each other. 

1. An electric pencil sharpener, comprising: a motor; a cutter holder rotatably driven by said motor; a cutter member secured to said holder to rotate therewith; a slidable rod disposed along the axis of said cutter holder, said slidable rod being displaceable by the tip of a pencil to be sharpened; a first switch disposed rearwardly of and contactable by said slidable rod, said first switch having three contact elements sequentially operated by said rod, said first switch being connected to said motor to control operation thereof; a second switch connected between an external power source and said first switch; wherein: a. in a first position of said second switch and first and second positions of said first switch, said motor is in an operative mode; b. in said first position of said second switch and a third position of said first switch, said motor is in an inoperative mode; c. in a second position of said second switch and in said first position of said first switch, said motor is in said operative mode; and d. in said second position of said second switch and in said second and third positions of said first switch, said motor is in said inoperative mode.
 2. An electric pencil sharpener according to claim 1, wherein in said first position of said first switch all three contact elements contact each other, in said second position of said first switch only two of said contact elements contact each other and in said third position of said first switch none of said contact elements contact each other.
 3. An electric pencil sharpener according to claim 1, wherein in said first position of said first switch and second of said contact elements contact each other, the third element being disengaged from contact with said first and second elements, in said second position of said first switch, said first and second elements are disengaged from each other and from said third element, and in said third position of said first switch said second and third contact elements are engaged with each other, said first element being disengaged from said second and third elements.
 4. A pencil sharpener according to claim 1, wherein in said first position of said first switch said three contact elements are disengaged from contact with each other, in said second position of said first switch, first and second of said contact elements are engaged with each other, the third element being disengaged from contact with said first and second elements, and in said third position of said first switch said first, second and third contact elements are in contact with each other. 